- Noun. A period into which a year is divided, historically based on the phases of the moon. In the Gregorian calendar there are twelve months: January, February, March, April, May, June, July, August, September, October, November and December.
- Noun. A period of 30 days, 31 days, or some alternation thereof.
- Noun. (obsolete, in the plural) A woman's period; menstrual discharge.